Using 1and1.com Servers, SMTP Mail is Limited - Local XAMPP Server Works As Expected

http://serverfault.com –
I'm starting to not like 1and1.com that much. I've used them for years, but mainly for simple sites without much need for configuration. I know there are better hosting companies out and I may go seeking them.
The problem here is that on my Local XAMPP server (sitting on a network with Comcast ISP), I have a PHP script that uses PEAR::Mail to send mail using MIME. The script works find locally with either smtp.1and1.com and corresponding credentials and smtp.gmail.com with corresponding credentials, using appropriate ports, etc.
1and1 tells me that I have to change the MX record on the do
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